When I was running the Sunless Citadel, the gnomish cleric of Olidammara (Trickery domain) used his disguise self to imitate undead. I don't remember the exact circumstances, but I think he wanted to look like a goblin skeleton. I let him do it, though obviously with the "recently dead" flavor so there wouldn't be the issue of transparency through the bones. I didn't particularly care how accurate of a representation of "true" undead he created; I just liked the idea and went with it, spooking whatever bad guys were there.
As an ongoing tactic, it will work against most creatures, but I would allow anyone with a good Knowledge(religion) or a good Spot check to see through a first level spell, yo.
As an ongoing tactic, it will work against most creatures, but I would allow anyone with a good Knowledge(religion) or a good Spot check to see through a first level spell, yo.